1. Field Of the Invention
The invention relates generally to printers using ink ribbons having multiple widthwise printing tracks and more particularly to a switching mechanism for selecting a desired track on the ink ribbon. The invention further relates to a printing mechanism for achieving a compact color printer using multi-track multi-color print ribbons.
2. Description of Related Technical Art
The color printing process or color printers commonly employ ink ribbons having multiple ink tracks each with a different color. A printer is shown in FIG. 10 which is capable of printing in color using an ink ribbon 90 which has three widthwise color tracks, 91, 92, and 93 which are black, red, and blue, respectively. Switching between the three tracks 91, 92, 93, is typically performed using driver such as a motor 21. The illustrated printer is a dot matrix type of printer in which a print head 81, which has a series of electrically actuated print pins, is mounted on a carriage 83 that reciprocates laterally along a main guide shaft 82 to form a series of image forming dots during printing. An example of track switching technology using a multi-color ink ribbon is disclosed in more detail in Japanese Laid-Open Patent Publication 3-41356, and is outlined further below.
Carriage 83 is moved back and forth along main guide shaft 82 by a carriage drive motor 85 typically using a timing belt 84. As head 81 is moved, printing along a path or line in the direction of travel is performed on recording paper 87 or other medium as desired, which is positioned on a platen 86. Three-color ink ribbon 90 is typically housed in a ribbon cassette 95, which rests on an appropriately shaped ribbon frame 96, here box-shaped. Ribbon frame 96 is moved or displaced up and down by a switching arm 23, which moves along a guide 22 fixed to a printer base 88, and as a result ribbon tracks 91, 92, and 93 are also moved up and down in front of print head 81, and selected for use. Switching arm 23 is pivoted up and down by a cam wheel 25 which is in turn driven or rotated by switching motor 21 using a gear 24, and the position of selected tracks 91, 92, and 93 can be confirmed using a position sensor 26 disposed on the cam wheel.
An alternative printer structure is shown in FIG. 11 in which an ink ribbon 90 is used having only two widthwise color tracks 91, which is black, and 92, which is red in this example, and print head 81 is driven along guide shaft 82 by a drive arm 30, which is rotated by carriage drive motor 85. Again, ribbon 90 is housed in a ribbon cassette 95 mounted on ribbon frame 96. Two solenoids, 31 and 32, are used to set or select either color track 91 or 92 in this printer structure as desired. First solenoid 31 is used to select upper track 91 of ribbon 90, by moving a setting rod 33. As a result of the rod 33 motion, ribbon frame 96 is pulled downward using a setting arm 34 which protrudes from ribbon frame 96.
When ribbon frame 96 moves downward, a spring 36 causes a setting hook 35 to be biased against and interlock with ribbon frame 96, which is then set or temporarily locked in this lower position. In this configuration, track 91 is selected and the color black is used by print head 81 during printing operations. When solenoid 32 pulls against setting hook 35 so as to resist the force of spring 36, setting hook 35 disengages its contact with ribbon frame 96 which is released to travel upward under the biasing action of a spring. This latter action results in track 92 being selected and the color red being used by print head 81 during subsequent printing operations.
Therefore, using the above configurations and general operating procedures, printing with a plurality of colors is facilitated using an ink ribbon on which a series of widthwise color tracks are formed.
Currently many printers are becoming increasingly compact with an eye to achieving portable use, while trying to maintain a multicolor printing capability. Such compact or portable printers must be particularly light in weight and have decreased power consumption, while also having low production costs. However, continuing to perform ribbon color track selection, as described above, using a motor, solenoid or other dedicated driver device, increases both the weight and power consumption of the printer. Aside from these drawbacks when using a heavy, power-consuming, drive system motor or solenoid, overall printer reliability is also decreased while production costs are increased due to an increased number of parts such as levers, hooks, and gears, employed in implementing such drivers.
At the same time, there is a demand for three or more colors instead of just two, which requires more complicated drive and control systems to be added to effect ink ribbon track selection the various tracks, thus, further aggravating the above problems.
What is needed is a technique for selecting different ink ribbon color tracks which does not employ specialized, heavy or excessively power consuming, track selection drivers. It is also desirable that any track selection system provide for efficient switching among three or more tracks with minimum complexity and few parts.